The Harlem Line trains start early, and the pavement by the Mount Kisco platform has to be open before the first one pulls in. joe valvano and sons works winter nights for exactly that reason — plowing drives and lots, shoveling walks and steps, spreading salt and sand where the cold bites hardest before sunrise. A storm in northern Westchester rarely ends politely; it tapers, then drops another two inches at four in the morning, and the truck goes back out. Nobody sees the work, which is the point: the pavement is black, the walk is gritty underfoot, the day goes ahead as planned. Mount Kisco, Bedford Hills, Katonah and Armonk are all on the night route.